How many amps would the circuit below draw? What if they were 2 kW, 3 kW and 4kW?

Anyone care to explain how you found your answer? Electricity stuff makes me feel totally inept. It always feels like I'm on the verge of understanding things and then I realize I don't know anything.

I'm trying to wire up the heat lamps for the paint booth and I need to know what size wire we'll need and what size breakers to use.

EDIT: It's 220v.

You will have 6 kW going thru the total circuit. 2kW on each of the three legs of the circuit.

The 6 kW is power. To determine the amperage (electric flow rate) , the resistance of the circuit will need to be known, or the voltage.

One watt is equal to one amp going across one ohm of resistance.

One Volt is the potential between two points flowing one amp dissappated as one watt (accross an one ohm resistance)

Thus to get your answer, we need either the voltage, across the circuit, or the resistance of the circuit.

If it is 200 volts, then:

6kW = 6000 Watts at 200 volts means 30 Amps of current.

200 Volts x 30 Amps = 6000 Watts

if 220 volts, then it is 27.3 Amps

if 120 Volts, then it is 50 Amps

Note how the current increases for a given power, as the voltage is reduced. Higher voltage means less amperage to consume the same watts (power)

Thus a 240 volt circuit can on a 20 Amp breaker can supply as much power as a 120 volt circuit running 40 Amps! The total watts on each circuit is the same maximum of 4800 watts. Less voltage, means higher current to get same power.


if you are talking heaters, the bottom line is power to the heater. By using a higher voltage, a smaller breaker or fuse is required for the same wattage (power). with higher voltages, smaller currents mean a smaller diameter wire can be used to power the heater, as the diameter of the wire is selected based on current, not voltage (the insulation on the wire determines its voltage rating)

hope that helps.

dave

PS if the lamps are run on 110 volt, and if you have a 220 v supply, you could run half the lamps off one leg of the 220 hot to nuetral, that will supply half the lamps, and repeat on the other half using the other "hot" half of the 220 line to neutral. Thus you will have 110 volts to the lamps, and will need two 30 amp breakers, one for each leg, Or if you have 220 volt heat lamps, wire directly to the 220 volts, using one 30 Amp breaker

In each case you will have about a 10% margin on the breaker amperage. (you might want more)

Wire selection will need be based on the current you run (amps) which will be determined by the voltage you select. Also the length of wire must be considered in the determination of diameter. A longer run of wire will require an increase in diameter.

So armed with the current (determined by voltage) and the length of wire, you should be able to look up the correct gage of wire on a chart. I generally go one size bigger for extra robustness, or for future expansion room for add on circuit, so keep that in mind.

Same holds true with the breaker, the 27.3 Amps required could work well with a 30 amp breaker, but I'd likely up rate it to 40 or 50 amps. Just be sure that the breaker is no bigger than the wire it must protect. If your wire is only good for 40 amps, do not install a 50 amp breaker. The breaker must be rated less than the wire, and the wire must be rated to carry the planned load, plus any future expansion.

Okay, what if they were wired in series?

Hi Marc
I did a similar project, 3 x 1000 watt.
My space confinmenets I used 3 curciuts to each hetaer #12, then these went to a splitter, then a #10 to fuse panel protected by a 30 or 40 amp breaker (been a few years), I had to do it this way because it was a constuction project not an add on, and wiring needed to be passed in advance, hence the splitter.
We have huge "codes" for paint shops, but I am sure you know the dos and don'ts in your area, explosion proof motor and heaters etc...all curciuts in bx or conduit (sp)
Regards
Joe

It would still be the same current draw, as the heat lamps have a rated wattage,and voltage, thus no matter how you wire them, you still have the same power requirement in total.

If they were however in series, if one went open circuit, they would all lose power. Kind of like cheap xmas lights where when one goes bad, and the whole set dies. You normally do not find circuits in buildings wired in series for this reason, one fault, and the whole thing goes down.


Also since this is a paint drying booth right? Some consideration should be given to explosion proof lamp fixtures, junction boxes, and if located in potential fume areas, the switch and breaker.

My thought on the heating lamps is if at all possible, maybe wire them on seperate switches, so you can control the amount, and location of heat, also save energy if all lamps are not needed.

if so, then all the lamps could be on one 40 Amp breaker, with heavy wire to handle say 40 Amps at 220 volts (this is more than is needed, but will allow future expansion without new wire / breaker, really only 30 Amp is needed) The 40+ amp rated wire however need be ran the entire system, even if you used three switches to divide the current into three 2000 watt sub-circuits.

The reason why you would keep using the heavy 40+ Amp rated wire, even on a section which is designed for only one third the entire circuit load (2000 W or about ten Amps at 200 volts) is that you must never use wire in any branch of a circuit that is rated less than the fuse or breaker protecting that circuit.

If you do not follow this rule, and use a smaller wire in one part of the circuit, that smaller wire in effect will become the fuse if you get a short circuit on that line. When a wire becomes the "fuse" it gets hot, and starts fires. The breaker amperage rating must always be the "weakest link" in the "chain" of the circuit. You would not be building to code otherwise, it is a safety issue.

The final circuit will be determined on if you will be running 110 or 220 volt heat lamps.

If 220 Volt, then 30 Amp minimum (recommend 40 Amp if available) breaker and wire rated higher than breaker amps for the circuit. Wire the two open ends on your diagram circuit too the 220 Hot, and Hot terminals. You can use one switch, but ideally it should be a double pole switch, as both wires will be hot, and you do not one wire still hot when switched off. So use a double pole switch, or use three of them, one on each 2000W branch.
A small breaker shut off box might be good

If 110 Volt, then wire the two open ends of the diagram off one leg of the hot and the other to nuetral using a 60 Amp (minimum) breaker, and wire rated at 60 amps. Also the switch must be rated at least at 60 amps! The switch need only be a single pole in the 110V circuit, as unlike the 220V circuit, one side of the 110V line is nuetral, there is only one Hot side, and the Hot wire is the only one that needs to be switched, so single pole here. Same option for one or three switches, all single poles.

You can see the advantage of the higher voltage 220V. lamps, they will require wire at half the rated amperage, that can save money in wire cost, also the switch need be rated at only half the amperage as that used on the lower voltage 110V.

That's why home ovens, and dryers typically run on 220V, cause they are high power users, that would require even thicker wires, and higher amperage breakers and switches if ran at 110V. Your 6kW heat lamps are in the power realm of electric ranges, and dryers, and should ideally be 220V, although 110V can be made to work.



One question???? I am assuming you are running on single phase. Are you? If you have three phase power (lucky you) you could wire the three branches on the lamps one on each phase and there are two methods of doing that, hot to hot, hot to hot, and hot to hot, verses hot to nuetral, hot to nuetral, and hot to nuetral ("Y" vs. "Delta" circuit types) You would be able to run 10-15 Amp breakers three each (usually sold as a three pole breaker) Or you could just run off one leg of the three phase, for all three lamps protected by one 30-40 Amp breaker.

By the way, 6000 Watts in heat lamps is equal to Eight h.p. (Horse Power) in heat lamps.

746 watts = one h.p.

And a 95 h.p. 2 liter is a 70.9 kW engine. Got to love electricity! Or to put it anouther way, your 2 liter 914 puts out the power of 709 each 100 Watt light bulbs!

One watt also equals one joule per second or 10 to the 7th power ergs per second.

The equevilence of the 2 liter motor to joules is 70.9 kjoules per second. One joule is one Newton meter, so the 2 liter engine puts out 70.9k newton meters per second.


Of note is that the lowly 914's 2 liter engine puts out an eye popping 7,090,000,000,000 ergs per second of power!!!

Any rate I drifted a bit here, wanted to have some 914 content.

its simple, divide your wattage by the voltage

watts/volts=amps

electric code only allows you to load a cicuit to 80 % of the breaker, so after you get your amp rating mutiply it by 1.25. then your wire sizes are the following 12 is for 20 amp, 10 is for up to 30 amps, 8 is up to 40 or 50 depending on you local intrepritations (sp), 6 is good to 70 ( normally breakered at 60 )

you will have to break the heaters in to smaller circuits unless you want to use big wire.